The present application relates to construction equipment, such as cranes. In particular, the present application relates to a crane having several unique and inventive aspects, such as a hydraulic boom hoist cylinder, a hydraulic circuit to control the hydraulic boom hoist cylinder, a multiple position wire rope guide, and a counter weight positioning mechanism. The present application also relates to a method of self-assembling the boom hoist cylinder crane.
Construction equipment, such as cranes or excavators, often must be moved from one job site to another. Moving a crane or an excavator can be a formidable task when the machine is large and heavy. For example, highway limits on vehicle-axle loads must be observed and overhead obstacles can dictate long, inconvenient routings to the job site.
One solution to improving the mobility of large construction machines, such as cranes, is to disassemble them into smaller, more easily handled components. The separate components can then be transported to the new job site where they are reassembled.
The typical practice has been to use an assist crane to disassemble the crane into the separate components. The assist crane is then used to load the components onto their respective transport trailers. Once at the new job site, another assist crane is used to unload the components and reassemble the crane. As the components for a large crane can weigh as much as 80,000 lbs., the capacity of the assist crane required represents a very significant transport expense.
As a result, designers have attempted to develop self-handling systems for assembling and disassembling cranes. The majority of the self-handling systems developed thus far have been directed to smaller cranes which need to be disassembled into only a few components.
The development of self-handling systems for larger cranes, however, has met with limited success. One reason for this is that larger cranes need to be disassembled into numerous components, thus requiring time-consuming disassembly and reassembly procedures. For example, a large capacity crane typically uses a complicated and cumbersome rigging system to control the angle of the boom. Boom rigging system components such as the equalizer, the backhitch, and wire rope rigging are heavy and difficult to disassemble for transport. Another reason for the limited success of prior art self-assembling cranes is that they typically rely on additional crane components that are used only for assembling and disassembling the crane. For example, some self-assembling cranes require additional wire rope guides and sheaves on the boom butt so that a load hoist line can be used with the boom butt to lift various crane components during the assembly process. An example of one prior art method for disassembling a typical large capacity crane is disclosed in U.S. Pat. No. 5,484,069.
It is therefore desirable to provide a crane and method of self-assembly which reduces the number of parts which must be derigged and removed to disassemble the crane for transport. In addition, it is desirable to eliminate redundant components which are only used during the crane assembly process.